The change is simple enough—just have to roll up your sleeves and apply a simple registry hack—but could make a big difference if you’ve already customised your logon wallpaper. To make the change, open up the registry editor and browse down to the following key:

HKLMSOFTWAREMicrosoftWindowsCurrentVersionAuthenticationLogonUI

Create a new DWORD called ButtonSet and give it a value between 0-2 (You’ll want to use 2 for darker backgrounds). You can delete the key or set it to 0 to revert back to the default setting, and the changes should be applied immediately.